MEMS sound transducer

1. A MEMS sound transducer, comprising:

a substrate having a back cavity;

a stator, the stator having a central portion suspending on the back cavity and at least two fixed arms extending from the center portion to the substrate and fixed on the substrate;

a movable cantilever, mounted to the substrate, at least partially facing the back cavity and disposed between two adjacent fixed arms; wherein, the movable cantilever has a fixed end mounted to the substrate and a free edge facing the fixed arms with space;

the free edge has a plurality of moving comb-fingers formed thereon;

the stator has a plurality of fixed comb-fingers formed on the fixed arms;

the moving comb-fingers and the fixed comb-fingers fit to each other to form a capacitor with an overlap area;

further comprising a back plate mounted on the substrate, the back plate spaced from the movable cantilever and formed a capacitive coupling with the movable cantilever; the back plate further comprising a plurality of through holes.

2. The MEMS sound transducer according to claim 1 , wherein, the stator has four fixed arms; and the MEMS sound transducer further has four movable cantilevers.

3. The MEMS sound transducer according to claim 1 , further comprising a spacer, the spacer is fixed to the substrate, and the fixed end of the cantilever is mounted on the substrate via the spacer.

4. The MEMS sound transducer according to claim 1 , wherein, a height of the cantilever along a vibrating direction is equal to that of the fixed arm.

5. The MEMS sound transducer according to claim 1 , wherein, a height of the cantilever is lower than that of the stator along a vibrating direction, the cantilever further comprises a protruding part extending from the free edge upward or downward in a vibrating direction; the height of the protruding part is equal to that of the fixed arm.

6. The MEMS sound transducer according to claim 1 , wherein, a height of the cantilever is lower than that of the stator along a vibrating direction, the cantilever further comprises a protruding part attached to the free edge at a center thereof; the height of the protruding part is equal to that of the stator.

7. The MEMS sound transducer according to claim 1 , wherein, the fixed arm has a top layer and a bottom layer, the top layer and the bottom layer are spaced from each other and electrically isolated from each other.

8. The MEMS sound transducer according to claim 7 , wherein, the stator further includes an insulation layer formed between the top layer and the bottom layer.

9. The MEMS sound transducer according to claim 7 , wherein, an air gap is formed between the top layer and the bottom layer.